1. Field of the Invention
The present invention relates to heat engines and more particularly to nitinol powered heat engines.
2. Description of the Prior Art
The inventor of the present invention is also the inventor of the Banks engine, U.S. Pat. No. 3,913,326 issued Oct. 21, 1975, which was the first and remains the only proven reliable nitinol engine. The "Background of the Invention" section of that patent sets forth in part the status of the prior art at the time of that invention. The "Summary of the Invention" section of that patent describes the thermodynamic working material as a thermally responsive memory material, such as nitinol, which is used to power the present invention.
Since the development of the Banks Engine, many investigators have studied the concept and tried to improve upon it but with little success. Probably the best summary of all of the subsequent work has been set forth in an article by William S. Ginell, Joseph L. McNichols, Jr. and John S. Cory, published in the May 1979 issue of Mechanical Engineering Magazine at page 28 entitled "Nitinol Heat Engines for Low Grade Thermal Energy Conversion". As stated therein "(A)ll the (nitinol heat) engine designs appear to fall into five catagories: offset crank, turbine, field, swash plate, and hydraulic engines. Of these five, operational examples of only the first three types have been reported" (p. 28). The art in the field of nitinol heat engines is very limited and prior to the present invention, none of the designs have proven to be one which could be utilized for productive work. As stated further in the article, "(A)lthough small nitinol heat engines have been built and operated, their efficiencies and output powers have been low and attempts to produce an engine of practical size have not been successful (p. 31)."
None of the prior art designs provide a physical arrangement that thermally cycles the powering material and changes phase simultaneously to produce unified power. All of the designs prior to the present invention change phase in steps, or successively, and obtain only a portion of the power potentially available in the machines during any particular time segment of a power cycle. Usable power, therefore has not been developed by prior art devices. Further, the only machine which has been successfully operated for a long period of time is the Banks engine.